Lubricating oil composition containing 2:1alpha-glycol borate compounds



United States LUBRICATING OIL COMPOSITION CONTAINING ZHWGLYCQL BORATE COMPOUNDS Samuel M. Darling, Lyndhnrst, and Chien-Wei Liao,

Cleveland, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio This invention relates to a lubricating oil composition comprising the reaction product of an a-alkylenediol with boric acid in the ratio of two moles of the diol to one mole of the boric acid.

One of the most serious problems encountered in the operation of internal combustion engines is the deposits which form progressively and accumulate on the surfaces within the combustion zone, on the cylinder head, piston top, sparkplugs and the intake and exhaust valves. These deposits are made more stubborn by the tetraethyl lead present in most gasoline fuels, because this not only contributes to the deposit but it also converts it from an essentially carbonaceous deposit to one comprising appreciable quantities of lead and lead compounds mixed therewith, such as lead sulfate, and lead oxide. The carbonaceous deposits act as a cementing agent for the lead deposits, and the lead deposits are more diflicult to remove than the carbon deposits. Thus, a deposit of this sort is more tenacious and troublesome than a purely carbonaceous deposit.

The nature of the lead-carbonaceous deposits is such that they are quite difficult to remove, once they have been built up. They are not attacked by the scavenging agents which are included in the fuel with the tetraethyl lead. Despite the fact that the amount of the deposits eventually levels off, after which there is no appreciable further increase, the presence of the built-up deposits interferes considerably with the operation of the engine, and it would be desirable both to prevent formation of deposits and to remove them after they have been formed. The disadvantageous effects of these deposits are well discussed in US. Patent No. 2,741,548 to Samuel M. Darling, Philip S. Fay and Lorraine S. Szabo.

atentO It has beenv proposed to attack such deposits by in- I corporating in the liquid leaded motor fuel an organic boron compound which is soluble in the fuel. The boron compound is thought to modify the action of the fuel in the engine, and to react with the deposits so that the adverse effects. due to the deposits are eliminated or markedly reduced.

It is known that the carbonaceous components of the deposits in the engine are built up not only from the gasoline but also from the oil, which enters the combustion,

system from the crankcase in various ways. This oil is in the liquid phase in the combustion zone of the engine, whereas the gasoline, of course, is in the vapor phase. However, it is essential that the boron compound be soluble in the medium in whichit is introduced into the.

engine. For use in lubricating oil, the solubility must be quite high, relative to that in gasoline, because more additive is needed in the lubricating oil to obtain an effect. Moreover, the stability of the boron compound against hydrolysis must be high, in view of the larger amounts of.

compound present, and the hydrolysis products must be soluble in the oil as well, since insoluble boron deposits in the crankcase and lubricated parts of the engine might be harmful and. certainly would be ditficult to remove.

Moreover, the boron compounds incorporated in liquidice leaded motor fuels are volatilizableunder the combustion zone conditions, and also exist in the vapor phase in the combustion zone. If such organic boron compounds were present in the oil, they would,,under the combustion zone conditions, nonetheless be expected to volatilize. Compounds having a much higher boiling point, are necessary for use in lubricating 'oils. Such compounds should also be stable in the presence of moisture. Because of this, it has not been possible to incorporate these compounds in the oil.

It has now been determined, in accordance with the invention, that the reaction products of boric acid with certain highly branched a-alkylene gylcols in the proportion of one mole boric acid to two moles of the a-alkylene glycol are oil-soluble, more moisture-stable, and have low volatility, provided the gylcol has at least eight carbon atoms up to about twenty carbon atoms. Engines operated with lubricating oils containing such boron compounds have improved performance. The deposits arereduced. The ignition temperature of such engine deposits as remain is increased, therefore repressing surface ignition. It is thought that the boron compounds react with the lead in the deposits forming lead borate, and that this does not act catalytically to the same extent because it has a. higher flow point than the lead oxide and lead sulfate usually present in such deposits. These additives are compatible with conventional lubricating oil additives.

The reaction products in accordance wtih the invention are defined by the following general formula:

0 R/ \B-0ROH where R and R are a-alkylene radicals having a straight or branched chain of from eight to twenty, preferably from eight to ten, carbon atoms, a chain of two carbon atoms linking the radicalto the When one of R R R and R, is hydrogen, preferably the R attached to the CH is branched, preferably tertiary. The R R R and R radicals can be straight-chain or branched alkylradicals; preferably at. least. one of R R R and R is branched,.preferably tertiary. Thus, R R5, R and R can be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl, secondary biityl, amyl, isoamyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, and

octadecyl radicals, taken in sufficient number to meet the requirements of the formula for the total number of carbon atoms. r

If one a-alkylene glycol is employed, one molecular species is obtainable from the walkylene glycol and boric acid. lf two a-alkylene glycols/ are employed, four molecular species are poss glycol and two mixed borates.

Typical of the compounds which come within the invention are the following:

ible, the two borates of each C CH1 It has already been indicated that when one a-glycol is employed, only one molecular species is formed, and that when a mixture of two is used, four molecular species are possible. It will be apparent from the above that more complex mixtures of reaction products can be obtained from mixtures of three and more a-diOlS. However, all of these are operative in the compositions of the invention.

The borate compounds of the invention are solids or liquids which are stable to moisture. The liquids and the solutions of the compounds in oil remain homogeneous and clear when stored in a moisture-saturated chamber for forty-eight hours at room temperature (25 C.). They are soluble in petroleum lubricating oils at very large concentrations. They are substantially involatile at crankcase temperatures.

These compounds can be prepared by mixing the reactants in the stoichiometric 2:1 molar ratios and heating them above 60 (3., up to about 150 C., on a and contents. Alternatively, the reactants can be refluxed in the stoichiometric ratios in dry benzene in a flask provided with a water condenser and a water-collecting; trap until the theoretical amount of water has been and tropically distilled. This permits use of a lower temperature. the trap. The benzene then is removed from the reaction mixture by distillation, and the residue vacuum-distilled or recrystallized.

The compounds numbered (1), 2) and (29) above were subjected to screening tests to determine oil solubility, moisture stability and volatility. Oil solubility was observed at a concentration of about 0.1% boron. Moisture stability was studied with both the undiluted liquid additive and an oil solution containing at least the equivalent of 0.1% boron. Samples had to remain visually unchanged with respect to homogeneity and clearness after being stored in a moisture-saturated chamber for forty-eight hours. Volatility was determined by the distillation characteristics of the compounds themselves. The data obtained appears in Table I:

The borate compounds of the invention can be used with any petroleum hydrocarbon oil of lubricatingviscosity. The SAE viscosities for lubricating oils range from No. 10 to No. 70. The neutral oils and refined oils, such as the acid-treated and solvent-extracted oils, are equally useful in the compositions of the invention. The oils may be blended from suitable bright stocks and finished neutral or refined oils of light and heavy viscosities. It is impossible hereto give a complete description or the various methods used in the preparation of lubricating oils, but reference is made to the'text by Georgi entitled Motor Oils and Engine Lubrication, published by Reinhold Publishing Corporation, New York (1950), chapter V, wherein the various types of lubricating oils are discussed fully. Any of the oils mentioned therein can be employed in the compositions of the invention.

Relatively large amounts of the organic borate compounds of the invention, in oils as compared to the amounts required in gasoline, are needed to give an improvement in engine performance. All proportions of the compounds are based on the amount of boron'in-the compound as a percent of the total oil composition, since it is the boron that is the active component in removing the deposit. At least 0.05% is the minimum] Use of amounts in excess. of 0.5% usually cannot be justified economically, and excessive amounts may lower the viscosity index.

The composition of the invention is prepared simply Examples 1 t0 3 Three lubricating oil compositions were prepared using a lubricating oil blend of 67% solvent-extracted neutral oil, 300 SSU at F. and 33% of a solvent-extracted,

The water removed is determined by the water in When the above oils were used in the crankcase of an internal combustion engine operating for a period of over seventy-two hours on nonboron-containing gasoline and the engine was then dismantled, the deposits in the combustion chamber were found to contain boron with the attendant advantages of the same in the deposit as discussed earlier.

The compositions were subject to the Falex E.P. test, run by the standard procedure, where the load on the hearing was increased automatically and the pressure reported was that registered at failure. The wear tests were run on the same equipment using a constant pressure on the bearing.

The data showed that the oil of the invention containing the boron compound tolerated higher pressure and produced less wear than either the corresponding blend without boron or the base oil alone, thereby indicating that there would be no adverse efiect by the use in crankcases of engines. 7

The extraordinary moisture stability of the compounds of the invention is explained by postulating the existence of a chelated structure, in which the tree OH group is attached to the boron by a semicovalent bond, thus:

There is much evidence to support this structure. Since this has not been definitely established, however, the compounds are not shown in this structural arrangement.

We claim: 1. Petroleum lubricating oil having dissolved therein a moisture-stable organic boron compound having the formula:

where R and R are a-alkylene groups having from eight to twenty carbon atoms having the structure:

the free valences being attached to oxygen, and R R R and R being selected from the group consisting of hydrogen and alkyl, at least three of R R R and R being alkyl, and the remaining R being selected from the group consisting of hydrogen and alkyl, the amount of said compound based on the weight of the lubricating loil being equivalent to from 0.1 to 0.5% by weight of oron.

2. Lubricating oil in accordance with claim 1 in which the boron compound is:

3. Lubricating oil in accordance with claim 1 in which the boron compound is:

CHQ- -0H= H- 0 CH;

B-0 CHOH O/ 21H: CHr--CH:

CH: t

4. Lubricating oil in accordance with claim 1 in which the boron compound is: 

1. PETROLEUM LUBRICATING OIL HAVING DISSOLVED THEREIN A MOISTURE-STABLE ORGANIC BORON COMPOUND HAVING THE FORMULA: 